State Wheatstone bridge principle and deduce it using Kirchhoff's rules.

Explanation

Principle of Wheatstone bridge. It state that if the ratio of the two resistance `((P)/(Q))` on the one edge is equal to the ratio of the two resistance `((R )/(S))` in another edge, then there will be no flow of current between the mid points of the two edges of resistance. Condition of balanced Wheatstone Bridge. `(P)/(Q) = (R )/(S)`